In the technological area of photovoltaics, there exist applications that require the efficient conversion of a narrowband optical input signal into an electrical output signal, for example by producing a direct current (DC) electrical output. In some of these applications, the narrowband optical input signal is provided by a laser or a light emitting diode.
Prior art devices for converting the optical input signal into the electrical output signal include photovoltaic single junction devices, which typically produce a low-voltage electrical output, which can be too constraining for designers. The prior art devices also include photovoltaic multi-junction devices that can have multiple photovoltaic junctions arranged in a same plane and electrically connected to each other in series. Such photovoltaic multi-junction devices can produce higher voltage output signal; however, they require that the multi-junctions have the same dimensions, be arranged symmetrically, and that the impinging narrowband input optical signal be shaped and directed towards the multi-junctions in a way that uniformly illuminates each junction. Further, such photovoltaic multi-junction devices can require complicated fabrication and assembly techniques including, for example, the need for a plurality of deep trenches with high aspect ratio etches in the various semiconductor layers, air bridge metal connectors, multi-level contacts and connections, thick doped semiconductor layers to minimize the sheet resistivity (for example for back contacts or top contacts), etc.
Therefore, improvements in transducer that convert an input optical signal into an output electrical signal are desirable.